Data transmission method by polling and terminal apparatus for use in the method

ABSTRACT

A data transmission method in which a transmission request is forwarded from a host apparatus to a terminal apparatus. When receiving the transmission request, the terminal apparatus forwards as communication request to the host apparatus. In this communication request, a timer value of asa system timer included in the terminal apparatus is incorporated. Having received the communication request including the timer value, the host apparatus establishes an ID for the terminal apparatus according to the timer value. Then, the host apparatus conducts polling for collecting data from the terminal apparatus using the established ID.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a data transmission method by pollingand a terminal apparatus for use in the method. In particular, itrelates to a method and a terminal apparatus in which an identifier (ID)of the terminal apparatus for polling can be changed easily.

In recent years, data transmission systems, in which a plurality ofterminal apparatuses are connected with a host apparatus to execute adata transmission between them, have been widely used. In thesetransmission systems, a plurality of terminal apparatuses are connectedsimultaneously to a communication line, and data transmission is carriedout by a host apparatus conducting polling of a corresponding terminalapparatus.

2. Description of the Related Art

Data transmission in a conventional method using the data transmissionsystems mentioned above has been carried out, in general, as describedbelow.

The host apparatus conducts polling of the respective terminalapparatuses using their respective IDs by asking if they have data to betransmitted to the host apparatus. Each terminal apparatus monitors theline for its own ID. If a terminal apparatus having data to betransmitted to the host apparatus detects its own ID, it forwards acommunication request to the host apparatus. Thus, communication betweenthe host apparatus and the terminal apparatus is established to transmitdata.

Identification information (identifier, referred to as an ID below) isunique to the respective terminal apparatus and is registered by thehost apparatus at an initial stage of the data transmission procedure.

Since IDs in a conventional system have been uniquely given to therespective terminal apparatus, as mentioned above, the followingproblems have arisen.

For example, when a system as described above is constructed, new IDsshould be determined for the respective terminal apparatus which will beconnected to a host apparatus of the system. In addition, the newlydetermined IDs of the respective terminal apparatus should be registeredto the host apparatus. These procedures to determine and register therespective IDs of the terminal apparatus in the data transmission systemare not easy and require the efforts of a system engineer. In addition,when introducing more terminal apparatuses to the system later, the sameprocedures mentioned above should be repeated to determine and registerthe IDs of the new terminal apparatuses.

Further, since terminal apparatuses incorporated in the system sometimesbreak down, the broken ones must be replaced. Thus, the determinationand registration of IDs mentioned above should be carried out again forthe replaced apparatuses. If an ID which is different from that of thebroken apparatus is determined at the replacement, ID management for thesystem becomes complicated, thus increasing the burden on a systemengineer.

As explained above, by uniquely and fixedly determining an ID for eachterminal apparatus, the time required for ID management increases and alarge effort is necessary to re-establish new IDs in the datatransmission system.

SUMMARY OF THE INVENTION

The present invention was made to overcome the above mentioned problemsof the prior art. Therefore, the object of the present invention is toprovide a data transmission method whose ID management is easier than aconventional method and which is able to omit a reestablishing procedureof a new ID when a terminal apparatus is replaced with a new one.

Another object of the present invention is to provide a terminal devicewhich is suitable for use in the data transmission method of the presentinvention.

In order to achieve the above-mentioned object, the present inventionprovides a data transmission method for transmitting data in a systemhaving a host apparatus (host station) and at least one terminalapparatus (terminal station) connected to the host apparatus. In thismethod, first, the host apparatus forwards a transmission request to theterminal apparatus. Then, corresponding to this transmission request,the terminal apparatus sends back a communication request to the hostapparatus. In this communication request, a timer value of a systemtimer, which is incorporated in the terminal apparatus, is included.Having received the communication request including the timer value, thehost apparatus establishes an ID for the terminal apparatus according tothe timer value. Then, the host apparatus conducts polling forcollecting data from the terminal apparatus using the established ID.

According to the above feature, the method of the present invention doesnot require fixed determination of an ID of the terminal apparatus, thusovercoming the problems of the prior art methods mentioned previously.In recent years, particularly, devices used to construct terminalapparatuses usually contain a system timer, and therefore, little effortis required to construct a terminal apparatus which can be used with thedata transmission method of the present invention.

In another feature of the present invention, the host apparatus comparestimer values of respective terminal apparatuses when the system includesa plurality of terminal apparatus and some of them forward communicationrequests simultaneously in response to a transmission request sent bythe host apparatus. Then, the host apparatus gives a priority to one ofthe terminal apparatuses according to the compared result andestablishes an ID for the terminal apparatus having a priority accordingto its timer value.

Due to the above feature, the present invention is able to give thepriority to one of the terminal apparatuses by a very easy procedure.Therefore, the host apparatus is not required to keep informationregarding which terminal apparatus has priority and other informationregarding the priority sequence among a plurality of terminalapparatuses. Accordingly, the present invention can flexibly deal withthe replacement of a terminal apparatus or addition of more terminalapparatus in a data transmission system.

In still another feature of the present invention, the timer valueitself is established as the ID.

In still another feature of the present invention, a terminal apparatusis provided which is suitable for use with the transmission methodsmentioned above. This terminal apparatus comprises a timer for countingtime intervals, a memory for storing a value of said timer when theterminal apparatus can communicate with the host apparatus, and acontroller for forwarding a reply to a transmission request which isreceived from the host apparatus, said controller incorporating saidtimer value into a reply and forwarding it to the host apparatus.

In still another feature of the present invention, a further terminalapparatus is provided which is suitable for use with the datatransmission methods mentioned above. This terminal apparatus iscomprised of a communication adapter connected with the host apparatusthrough a communication line and a portable terminal which isconnectable with the host apparatus through said communication adapter,said portable terminal including, a timer for counting time intervals, amemory for storing a value in said timer when the terminal apparatus cancommunicate, and a controller for forwarding a reply to a transmissionrequest which is received from the host apparatus, said controllerincorporating said timer value into the reply and forwarding it to thehost apparatus through said communication adapter.

In still another feature of the present invention, a host apparatus isprovided which is suitable for use with the data transmission methodsmentioned above. This host apparatus is comprised of a communicationcontroller for forwarding a transmission request to said terminalapparatus and for receiving from said terminal apparatus a replycorresponding to the transmission request, an identification informationestablishing unit for extracting a timer value obtained from a timercontained in said terminal apparatus from the reply, which is receivedfrom the terminal apparatus by said communication controller, and forestablishing identification information for the terminal apparatusaccording to the extracted timer value, and a polling unit forimplementing polling to the terminal apparatus using the identifyinginformation established by said identification information establishingunit.

According to the above mentioned features, a user of the terminalapparatus and the host apparatus is not required to execute special andcomplicated operations in order to establish identification informationof each terminal apparatus. Therefore, the present invention can greatlyreduce the operational difficulties of the data transmission system.

BRIEF EXPLANATION OF DRAWINGS

The above object and features of the present invention will be moreapparent from the following description of the preferred embodimentswith reference to the accompanying drawings, wherein:

FIG. 1 is a view illustrating a data transmission system according toone embodiment of the present invention;

FIG. 2 is a view illustrating a portable terminal used in the datatransmission system shown in FIG. 1;

FIG. 3 is a block diagram showing the structures of a portable terminaland a communication adapter used in the data transmission system shownin FIG. 1;

FIG. 4 is a block diagram showing the structure of a host apparatus usedin the data transmission system shown in FIG. 1;

FIG. 5 is a time-chart showing the communication procedure between ahost apparatus and a terminal apparatus according to one embodiment ofthe present invention;

FIG. 6 is a time-chart showing the communication procedure between ahost apparatus and a terminal apparatus according to another embodimentof the present invention;

FIG. 7 is a flowchart showing the communication procedure between a hostapparatus and a terminal apparatus according to one embodiment of thepresent invention;

FIG. 8 is a flowchart showing the procedure for forwarding acommunication request from a terminal apparatus to a host apparatusaccording to one embodiment of the present invention;

FIG. 9 is a view showing an example structure of a transmission packetaccording to one embodiment of the present invention;

FIG. 10 is a flowchart showing polling operation by a host apparatusaccording to one embodiment of the present invention; and

FIG. 11 is a view showing a table indicating the relation betweenterminal apparatus and their IDs stored in the host apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows an example of data transmission system according to oneembodiment of the present invention. As shown in FIG. 1 a plurality ofterminal apparatuses (terminal station) 2 a, 2 b, . . . 2 n may beconnected with a host apparatus (host station) 4 through a communicationline 6. In the case shown in FIG. 1, the terminal apparatuses 2 a, 2 b,. . . 2 n are serially connected with each other with respect to thehost apparatus 4.

In one embodiment, host apparatus 4 comprises a host computer such as ageneral purpose computer, minicomputer or a workstation, and eachterminal apparatus 2 a, 2 b, . . . or 2 n is comprised of acommunication adapted 10 and a hand-held type portable terminal 8 asshown in FIG. 2. In another embodiment, each terminal apparatus maycomprise a personal computer. In still another embodiment, each terminalapparatus may comprise a POS (point-of-sale) terminal. In a furtherembodiment, a hand-held type portable terminal, a personal computer anda POS terminal may coexist as the terminal apparatuses.

As mentioned above, in the embodiment shown in FIG. 1, each terminalapparatus 2 (2 a, 2 b, . . . or 2 n) comprises a hand-held type terminaldevice (referred to as portable terminal, below) 8 and a communicationadapter 10. Portable terminal 8 is disconnectable from terminal adapter10 and it is usually carried by a user to collect data at a desiredplace. The collected data are stored in this portable terminal 8temporarily. The communication adapter (or a connection adapter) 10 isusually placed at a particular place and connected to the communicationline, for example, a telephone line.

The portable terminal 8 is carried for use by a user, and therefore, isdriven by a battery incorporated therein as a power supply. As shown inFIG. 2, each portable terminal 8 is a hand-held terminal and comprisesan input part 12 for inputting various kinds of information by a userand a display part 14 for displaying, for example, inputted informationand instructions. Various kinds of input devices have been known such asa key board and a touch panel. Since the structural differences betweenthese input devices are not directly related to the implementation ofthe present invention, the structure of such an input device will not bedescribed in detail here.

The terminal apparatus 2 is used typically as follows. A user carriesthe portable terminal 8 when he or she is collecting data, for example,in a store or a warehouse. The collected data are input and storedtemporarily into the portable terminal 8. When a certain amount of datais accumulated in the portable terminal 8, or, for example, at apredetermined time, the user moves to a particular place, where theconnection adapter 10 is placed, and inserts terminal 8 into the adapter10 to start data transfer to the host apparatus 4. The connectionadapter 10 is not always placed at a particular place. It may be carriedby the user and fixed to a communication line, for example, a telephoneline whenever he or she wants to transmit data. Thus, the user cantransfer data to the host apparatus through a telephone line from anyplace where a telephone is available.

It is also possible to use radio-communication system for transmittingdata from portable terminal 8 to the host apparatus 4 by suitablysetting the feature of the communication adapter 10. In this case, theuser can send data to the host apparatus 4 from any place whereradio-communication is possible.

The portable terminal 8 is advantageous in that a user can input anddisplay information through it while it is carried. Therefore, it isconveniently used for stock management of stores or warehouses, shippingmanagement of luggage, inspection of power meters, etc. In the case ofstock management, for example, a user can input a name of an item(including item codes) and a stock number for each item in a store whilecarrying a portable terminal. As such, stock information can becollected by inputting necessary data into the portable terminal.

The collected data are transferred to the host apparatus, for example,host computer, and they are processed to obtain necessary information. Amethod that uses a communication adapter for data transmission from aportable terminal to a host computer is widely known. In this method, aportable terminal is inserted into a communication adapter, which isconnected to a host computer through a communication line, andinformation stored in the portable terminal is transferred to the hostcomputer through the communication adapter. A connector for forwardingand receiving information is provided, respectively, for each of theportable terminals and the adapters.

FIG. 3 is a block diagram showing the internal structure of a portableterminal 8 and a communication adapter 10 according to one embodiment ofthe present invention.

The portable terminal 8 includes a control unit (CPU) 81, a clock (CLK,real-time clock) 82, a memory 83 for storing inputted information andoperational programs, a display control unit (D-CONTROL) 84, and acommunication control unit (C-CONTROL) 85. In addition, a connectingunit 86 having a light emitting device and a light receiving device isprovided to the portable terminal 8.

On the other hand, the communication adapter 10 is provided with aconnecting unit 101 having a light receiving device and a light emittingdevice, a communication control unit (C-CONTROL) 102, anddriver/receiver units 103 and 104 for forming an interface to thecommunication line 6.

As shown in FIG. 3, the connecting unit 86 in portable terminal 8 andthe connecting unit 101 in communication adaptor 10 form an opticalcoupling for data transfer.

Since the portable terminal 8 is frequently installed into and removedfrom the communication adapter 10, the connection part between themmight be easily broken if it is made from a mechanical connector.Therefore, a non-contact connector using an optical coupling ispreferable.

Once the portable terminal 8 is installed into the communication adapter10, the necessary steps for establishing a communication between themare carried out in the respective communication control units 85 and102. When communication between portable terminal 8 and communicationadapter 10 becomes possible, information stored in memory 83 of portableterminal 8 is read out and transferred to host apparatus 4 throughdriver 103 in communication adapter 10 and communication line 6. Thus,collected information in portable terminal 8 is transferred to the hostapparatus 4.

In one embodiment of the present invention, CPU 81 in portable terminal8 has an ability to establish its ID for use in polling operation withthe host apparatus, according to a system timer value obtained from realtime clock 82. In actuality, once the portable terminal 8 has beenactivated and installed into communication adapter 10, CPU 81 observeswhen the present terminal can communicate through the communicationadapter 10. As soon as the portable terminal can communicate, CPU 81finds the value of the system timer at this moment from CLK 82 andstores it in memory 83 as an ID value or information for determining anID of this portable terminals.

FIG. 4 shows the internal structure of the host apparatus 4. As shown,the host apparatus 4 is provided with a control unit (CPU) 41 forcontrolling the operation of this apparatus, a communication controlunit (C-CONTROL) 42 for controlling the communication with portableterminals through the communication line 6, an ID establishing unit 43for determining an ID for each portable terminal according to theinformation received from the portable terminal 8, and a memory unit 44for storing information received from portable terminals 8 and programsfor operating the apparatus itself. The control unit 41 also controls apolling operation between the host apparatus and terminal apparatus 2connected to this host apparatus through communication line 6. Thedetailed operation of the respective units will be described later.

Next, the polling operation between the host apparatus 4 and terminalapparatus 2, according to the present invention, will be describedbelow.

FIG. 5 is a time chart for explaining the transmission procedure betweenterminal apparatus 2 and the host apparatus 4. When collectinginformation from the terminal apparatus, host apparatus 4 forwards atransmission request on the communication line 6. This transmissionrequest is to ask if any terminal on the line has data to be transferredto the host, and therefore, the request is not forwarded to a particularterminal but to every terminal apparatus on the communication line. As aresult, any terminal apparatus connected to the communication line iscapable of receiving the transmission request from the host apparatus 4simultaneously as long as it can communicate.

Once terminal apparatus 2 can communicate, the system timer value atthis moment is determined by CPU 81 from clock 82 and stored in memory83, as shown in FIG. 5. Then, terminal apparatus 2 monitors the line fora transmission request from host apparatus 4. When terminal apparatus 2receives a transmission request from host apparatus 4, it sends acommunication request back to host apparatus 4. This communicationrequest comprises a transmission packet in which the system timer valueis incorporated. A detailed explanation of the system timer value willbe given later.

When host apparatus 4 receives the communication request from terminalapparatus 2, the system timer value contained in the transmission packetis detected and set to be the ID (identifier) of terminal apparatus 2,which sent the transmission packet, by ID-establishing unit 43. Then,host apparatus 4 implements a polling operation according to the ID thusdetermined.

Terminal device 2, which has forwarded the communication request to hostapparatus 4, monitors the polling operation from host apparatus 4 andwaits until its ID is included in the polling operation. When terminalapparatus 2 detects its ID in the polling operation, it forwardscollected information stored in memory 83 to host apparatus 4. In a casewhere its own ID is not included in the polling operation, terminalapparatus 2 waits until the next transmission request arrives.

The transmission procedure shown in FIG. 5 is simplified in the casewhere only one terminal apparatus 2 is connected to communication line 6and sends out a transmission request to host apparatus 4. Usually,however, a plurality of terminal apparatuses are connected to sendtransmission requests simultaneously to host apparatus 4. The time chartshown in FIG. 6 corresponds to such a case.

When a plurality of terminal apparatus 2 are connected to communicationline 6, host apparatus 4 may receive a plurality of communicationrequests from these terminal apparatus simultaneously since atransmission request from host apparatus 4 is not intended to beforwarded to a particular terminal apparatus 2. When receiving aplurality of communication requests from terminal apparatus 2, hostapparatus 4 compares the respective received system timer values witheach other and detects the oldest system timer value among them. Then,host apparatus 4 selects the terminal apparatus 2, which forwarded theoldest system timer value, to give it priority.

Once the priority has been given to a particular terminal apparatus, theID for this apparatus is established according to the timer value ofthis apparatus and polling is conducted using this ID to the respectiveterminal apparatus in the same manner as mentioned with reference toFIG. 5.

FIG. 7 is a flowchart for showing the procedure to obtain a system timervalue in a terminal apparatus. A terminal apparatus is activated andinstalled into communication adapter at step 701. At step 702, it isdetermined if the terminal apparatus can communicate. In case that theterminal apparatus can communicate, the present value of a system timercontained in this terminal apparatus is obtained at step 703 and storedinto a memory at step 704.

FIG. 8 is a flowchart for showing the procedure to transfer data, storedin the terminal apparatus, to the host apparatus.

When the terminal apparatus can communicate, as shown in step 801, itbegins to watch for a transmission request from the host apparatus atstep 802. If the transmission request is received, whether or not theterminal apparatus has data to be forwarded to the host apparatus isdetected at step 803. If data is to be forwarded, the system timer valuestored in the memory of the terminal apparatus is read out at step 804and incorporated into a transmission packet at step 805.

FIG. 9 shows one example of the transmission packet. In this example, astart bit and a stop bit are provided in the front region 91 and in theend region 95 of this packet. After the start bit region 91, a region 92for holding a system timer value is provided. Accordingly, the systemtimer value read out from the memory is written into this region 92. Inthe data region 93, the data to be transferred to the host apparatus arewritten. The data for making this packet to be a communication requestalso written into this region 93. A parity bit region 94 is providedafter the data region 93.

The system timer value having been incorporated into the packet as shownin FIG. 9, the terminal apparatus forwards the transmission packet tothe host apparatus as the communication request at step 806. Then, theterminal apparatus waits for polling from the host apparatus, at step807. When polling is detected, the terminal apparatus determines if itsown ID is included in the polling, at step 808. If its own ID isincluded in the polling, the terminal apparatus forwards the collecteddata to the host apparatus, at step 809.

FIG. 10 is a flowchart showing the polling procedure by the hostapparatus. At step 1001, the host apparatus forwards a transmissionrequest to a plurality of terminal apparatuses connected to thecommunication line to ask if they have information to be forwarded tothe host apparatus. After having forwarded the transmission request, thehost apparatus determines if it has received any communication requestfrom the terminal apparatus at step 1002. If no communication request isreceived, the host apparatus forwards the transmission request again. Onthe other hand, if a communication request is received at step 1002 fromany of the terminal apparatus, the host apparatus checks if anothercommunication request is received for the transmission request fromother terminal apparatus at step 1003. Because a plurality of terminalapparatuses are connected to the communication line and a transmissionrequest is not forwarded to a particular terminal apparatus, the hostapparatus may receive a plurality of communication requestssimultaneously from several terminal apparatuses.

If the host apparatus receives a plurality of communication requestssimultaneously, the host apparatus compares the system timer valuescontained in transmission packets from the respective terminal apparatuswith each other, at step 1004. Since the system timer values containtime-relating information, one embodiment of the present inventionselects the oldest system timer value according to the comparison andgives the priority to the terminal apparatus which has forwarded thetransmission packet having the oldest system timer value, at step 1005.

When a terminal apparatus has the oldest system timer value, thisapparatus indicates that it was connected to a communication adapterbefore any other terminal apparatus was connected to communicationadapters. After the terminal apparatus has finished forwarding data tothe host apparatus, it does not respond to a new transmission requestfrom the host apparatus since it has no data to forward, and therefore,no communication request should be forwarded to the host apparatus.Accordingly, by giving a priority to a terminal apparatus whichforwarded the oldest timer value, data collection can be executed for aterminal apparatus which was connected to a communication adapter beforeany other terminal apparatus was connected to terminal adapters.

When the priority is given to a particular terminal apparatus asmentioned above, the host apparatus extracts the system timer valueincorporated into the transmission packet and establishes an ID for theterminal apparatus according to the extracted system timer value, atstep 1006. In actuality, the system timer value itself is established asthe ID.

If the ID has already been registered in a table mentioned later, a newID establishment is not required to be conducted again. The details ofthis will be explained later with referring to FIG. 11.

Once the ID is established as mentioned above, the host apparatusconducts polling according to the established ID, at step 1007. Theterminal apparatus having the ID forwards data corresponding to thepolling, and then, the host apparatus receives the data, at step 1008.

As mentioned above, according to the present embodiment, an ID given tothe respective terminal apparatus is not peculiar to the apparatusitself, but can be varied at a proper occasion. In addition, since thepresent embodiment establishes the ID by utilizing a timer value of asystem timer which is usually provided in any terminal apparatus,additional hardware is not required to establish the ID. Further, thepresent embodiment does not require a fixed ID peculiar to each terminalapparatus and, therefore software for forming the ID becomes simple. Inorder to obtain the timer value, one embodiment of the present inventiononly requires that a portable terminal be set to a communicationadapter. However, this is not a special effort to obtain the ID sincethis is required to establish a communication between the portableterminal and a host. As a result, the present embodiment can set an IDfor a portable terminal almost automatically by simply installing theremote terminal into a communication adapter, which installing has beenrequired also in a conventional data transmission system. Therefore, thepresent embodiment greatly improves the utility of the portable terminalfor the users of this terminal.

In the above mentioned embodiment, it may be possible that a pluralityof terminal apparatus have the same timer value with each othersimultaneously. However, this situation can be neglected for the reasonsmentioned below.

In the data transmission system according to the present embodiment, notmore than 20 portable terminals are connected simultaneously to acommunication line. The probability that more than one portableterminals are simultaneously connected to the line can be consideredvery small due to the small number of the portable terminals. Inaddition, by measuring the system timer value to a several places ofdecimals, the probability that more than one portable terminals have thesame system timer values simultaneously can be reduced to a value whichcan be considered to be almost zero. Such a precise measurement of thesystem timer value is possible with a portable terminal in the presentsituation.

In the above embodiment, a portable terminal is used as a terminalapparatus, however, the present invention is applicable to a datatransmission system having a plurality of personal computers as terminalapparatuses. In this case, the personal computer is not set to acommunication adapter. It is, however, possible to program the personalcomputer to obtain the system timer value when it is turned on.

In the above mentioned embodiments, the host apparatus establishes an IDfor a terminal apparatus using a system timer value itself. For securityreasons, this system timer value can be processed to obtain an ID. Or, aparticular arithmetic operation can be applied to the system timer valueto obtain an encrypted ID. This operation or processing to obtain theencrypted ID from the system timer value can be carried out in eitherthe portable terminal 8 or the host apparatus 4.

FIG. 11 shows an example of a table which is stored in a memory of ahost apparatus. In the above mentioned embodiment, the ID establishmentis carried out every time a transmission request is forwarded to aterminal apparatus. However, a situation arises where the second orthird ID setting is not always necessary once an ID has beenestablished.

In such a case, for example, the portable terminal is formed orprogrammed so that the system timer value stored in a memory is notreset, once the portable terminal can communicate, unless it is removedfrom a communication adapter. Therefore, once an ID has been establishedfor a certain portable terminal, polling using the ID should beconducted until the portable terminal is removed from the communicationadapter.

In order to deal with the above case, the table shown in FIG. 11 isstored in a memory of the host apparatus. Then, when receiving acommunication request, the host apparatus determines if the system timervalue contained in the communication request has already been registeredin the table as an ID. If the received system timer value has not beenregistered, an ID is established according the received system timervalue. On the contrary, if the system timer value has already beenregistered in the table, no further ID establishing process isconducting.

As explained hereinbefore using various embodiments, the datatransmission method according to the present invention need notestablish an ID fixed to a respective terminal apparatus. Therefore, thepresent invention is able to save time and labour which is required toestablish and re-establish an ID for a respective terminal apparatus. Inaddition to this, the ID management process becomes simple according tothe present invention.

The respective terminal apparatus uses a system timer value, derivedfrom a timer contained therein, to form its own ID, thus easilyestablishing its own ID. In case that a terminal apparatus including asystem timer is used, additional hardware is not necessary to establishan ID.

Particularly, if a portable terminal, which necessitates a communicationadapter, is used, its own ID can be formed according to a system timervalue obtained at the moment the portable terminal is set into theadapter. Therefore, a user is not required to practice any specialeffort for establishing the ID. This is because the portable terminalmust be set into the communication adapter whenever a communication isrequired between the portable terminal and a host apparatus.

In case that a plurality of communication requests are forwarded to thehost apparatus, priority is given to a particular terminal apparatusaccording to a timer value. If the respective terminal apparatuses havefixed IDs as is the case of the prior art data transmission method,priority is given to a predetermined terminal apparatus. However,according to the present invention, the ID of a terminal apparatus isvariable, and therefore, giving priority according to timer values,which form the respective IDs, is very advantageous. Especially, bygiving priority in sequence from the oldest timer value, the prioritycan be transferred one after another among a plurality of terminalapparatuses.

What is claimed is:
 1. A terminal apparatus for use in data transmissionwith a host apparatus, comprising: a timer; a memory for storing a valueof said timer when the terminal apparatus can communicate with the hostapparatus; and a controller for forwarding a reply to a transmissionrequest which is received from the host apparatus, said controllerincorporating said timer value into the reply as identificationinformation of said terminal apparatus and forwarding it to the hostapparatus.
 2. The terminal apparatus according to claim 1, wherein saidterminal apparatus comprises a personal computer.
 3. The terminalapparatus according to claim 1, wherein the terminal apparatus cancommunicate when it is turned on.
 4. A terminal apparatus, for use indata transmission with a host apparatus, comprising: a communicationadapter connected with the host apparatus through a communication line;and a portable terminal which is connectable with the host apparatusthrough said communication adapter, said portable terminal including, atimer; a memory for storing a value of said timer when the terminalapparatus can communicate; and a controller for forwarding a reply for atransmission request which is received from the host apparatus, saidcontroller incorporating said timer value into the reply asidentification information of said portable terminal apparatus andforwarding it to the host apparatus through said communication adapter.5. The terminal apparatus according to claim 4, wherein said portableterminal is a hand-held terminal.
 6. The terminal apparatus according toclaim 4, wherein said terminal apparatus can communicate with the hostapparatus when the portable terminal is connected with the communicationadapter.
 7. A terminal apparatus, to be attached to a communicationadapter, which transmits data to and from an external device through thecommunication adapter, comprising: a timer; a memory for storing a valueof the timer at the time the terminal apparatus can communicate; and acontroller for forwarding a communication request to the external devicewhen the terminal apparatus receives a transmission request from theexternal device, wherein the controller sends the timer value stored inthe memory as identification information of said terminal apparatus withthe communication request.
 8. The terminal apparatus according to claim7, wherein the memory stores a value of the timer at the time when theterminal apparatus is attached to the communication adapter.
 9. Theterminal apparatus according to claim 7, wherein the memory stores avalue of the timer at the time when the terminal apparatus is turned on.